// MIT License:
//
// Copyright (c) 2010-2013, Joe Walnes
//               2013-2014, Drew Noakes
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

/**
 * Smoothie Charts - http://smoothiecharts.org/
 * (c) 2010-2013, Joe Walnes
 *     2013-2014, Drew Noakes
 *
 * v1.0: Main charting library, by Joe Walnes
 * v1.1: Auto scaling of axis, by Neil Dunn
 * v1.2: fps (frames per second) option, by Mathias Petterson
 * v1.3: Fix for divide by zero, by Paul Nikitochkin
 * v1.4: Set minimum, top-scale padding, remove timeseries, add optional timer to reset bounds, by Kelley Reynolds
 * v1.5: Set default frames per second to 50... smoother.
 *       .start(), .stop() methods for conserving CPU, by Dmitry Vyal
 *       options.interpolation = 'bezier' or 'line', by Dmitry Vyal
 *       options.maxValue to fix scale, by Dmitry Vyal
 * v1.6: minValue/maxValue will always get converted to floats, by Przemek Matylla
 * v1.7: options.grid.fillStyle may be a transparent color, by Dmitry A. Shashkin
 *       Smooth rescaling, by Kostas Michalopoulos
 * v1.8: Set max length to customize number of live points in the dataset with options.maxDataSetLength, by Krishna Narni
 * v1.9: Display timestamps along the bottom, by Nick and Stev-io
 *       (https://groups.google.com/forum/?fromgroups#!topic/smoothie-charts/-Ywse8FCpKI%5B1-25%5D)
 *       Refactored by Krishna Narni, to support timestamp formatting function
 * v1.10: Switch to requestAnimationFrame, removed the now obsoleted options.fps, by Gergely Imreh
 * v1.11: options.grid.sharpLines option added, by @drewnoakes
 *        Addressed warning seen in Firefox when seriesOption.fillStyle undefined, by @drewnoakes
 * v1.12: Support for horizontalLines added, by @drewnoakes
 *        Support for yRangeFunction callback added, by @drewnoakes
 * v1.13: Fixed typo (#32), by @alnikitich
 * v1.14: Timer cleared when last TimeSeries removed (#23), by @davidgaleano
 *        Fixed diagonal line on chart at start/end of data stream, by @drewnoakes
 * v1.15: Support for npm package (#18), by @dominictarr
 *        Fixed broken removeTimeSeries function (#24) by @davidgaleano
 *        Minor performance and tidying, by @drewnoakes
 * v1.16: Bug fix introduced in v1.14 relating to timer creation/clearance (#23), by @drewnoakes
 *        TimeSeries.append now deals with out-of-order timestamps, and can merge duplicates, by @zacwitte (#12)
 *        Documentation and some local variable renaming for clarity, by @drewnoakes
 * v1.17: Allow control over font size (#10), by @drewnoakes
 *        Timestamp text won't overlap, by @drewnoakes
 * v1.18: Allow control of max/min label precision, by @drewnoakes
 *        Added 'borderVisible' chart option, by @drewnoakes
 *        Allow drawing series with fill but no stroke (line), by @drewnoakes
 * v1.19: Avoid unnecessary repaints, and fixed flicker in old browsers having multiple charts in document (#40), by @asbai
 * v1.20: Add SmoothieChart.getTimeSeriesOptions and SmoothieChart.bringToFront functions, by @drewnoakes
 * v1.21: Add 'step' interpolation mode, by @drewnoakes
 * v1.22: Add support for different pixel ratios. Also add optional y limit formatters, by @copacetic
 * v1.23: Fix bug introduced in v1.22 (#44), by @drewnoakes
 * v1.24: Fix bug introduced in v1.23, re-adding parseFloat to y-axis formatter defaults, by @siggy_sf
 * v1.25: Fix bug seen when adding a data point to TimeSeries which is older than the current data, by @Nking92
 *        Draw time labels on top of series, by @comolosabia
 *        Add TimeSeries.clear function, by @drewnoakes
 * v1.26: Add support for resizing on high device pixel ratio screens, by @copacetic
 * v1.27: Fix bug introduced in v1.26 for non whole number devicePixelRatio values, by @zmbush
 * v1.28: Add 'minValueScale' option, by @megawac
 *        Fix 'labelPos' for different size of 'minValueString' 'maxValueString', by @henryn
 */

;
(function(exports) {

    var Util = {
        extend: function() {
            arguments[0] = arguments[0] || {};
            for (var i = 1; i < arguments.length; i++) {
                for (var key in arguments[i]) {
                    if (arguments[i].hasOwnProperty(key)) {
                        if (typeof(arguments[i][key]) === 'object') {
                            if (arguments[i][key] instanceof Array) {
                                arguments[0][key] = arguments[i][key];
                            } else {
                                arguments[0][key] = Util.extend(arguments[0][key], arguments[i][key]);
                            }
                        } else {
                            arguments[0][key] = arguments[i][key];
                        }
                    }
                }
            }
            return arguments[0];
        }
    };

    /**
     * Initialises a new <code>TimeSeries</code> with optional data options.
     *
     * Options are of the form (defaults shown):
     *
     * <pre>
     * {
     *   resetBounds: true,        // enables/disables automatic scaling of the y-axis
     *   resetBoundsInterval: 3000 // the period between scaling calculations, in millis
     * }
     * </pre>
     *
     * Presentation options for TimeSeries are specified as an argument to <code>SmoothieChart.addTimeSeries</code>.
     *
     * @constructor
     */
    function TimeSeries(options) {
        this.options = Util.extend({}, TimeSeries.defaultOptions, options);
        this.clear();
    }

    TimeSeries.defaultOptions = {
        resetBoundsInterval: 3000,
        resetBounds: true
    };

    /**
     * Clears all data and state from this TimeSeries object.
     */
    TimeSeries.prototype.clear = function() {
        this.data = [];
        this.maxValue = Number.NaN; // The maximum value ever seen in this TimeSeries.
        this.minValue = Number.NaN; // The minimum value ever seen in this TimeSeries.
    };

    /**
     * Recalculate the min/max values for this <code>TimeSeries</code> object.
     *
     * This causes the graph to scale itself in the y-axis.
     */
    TimeSeries.prototype.resetBounds = function() {
        if (this.data.length) {
            // Walk through all data points, finding the min/max value
            this.maxValue = this.data[0][1];
            this.minValue = this.data[0][1];
            for (var i = 1; i < this.data.length; i++) {
                var value = this.data[i][1];
                if (value > this.maxValue) {
                    this.maxValue = value;
                }
                if (value < this.minValue) {
                    this.minValue = value;
                }
            }
        } else {
            // No data exists, so set min/max to NaN
            this.maxValue = Number.NaN;
            this.minValue = Number.NaN;
        }
    };

    /**
     * Adds a new data point to the <code>TimeSeries</code>, preserving chronological order.
     *
     * @param timestamp the position, in time, of this data point
     * @param value the value of this data point
     * @param sumRepeatedTimeStampValues if <code>timestamp</code> has an exact match in the series, this flag controls
     * whether it is replaced, or the values summed (defaults to false.)
     */
    TimeSeries.prototype.append = function(timestamp, value, sumRepeatedTimeStampValues) {
        // Rewind until we hit an older timestamp
        var i = this.data.length - 1;
        while (i >= 0 && this.data[i][0] > timestamp) {
            i--;
        }

        if (i === -1) {
            // This new item is the oldest data
            this.data.splice(0, 0, [timestamp, value]);
        } else if (this.data.length > 0 && this.data[i][0] === timestamp) {
            // Update existing values in the array
            if (sumRepeatedTimeStampValues) {
                // Sum this value into the existing 'bucket'
                this.data[i][1] += value;
                value = this.data[i][1];
            } else {
                // Replace the previous value
                this.data[i][1] = value;
            }
        } else if (i < this.data.length - 1) {
            // Splice into the correct position to keep timestamps in order
            this.data.splice(i + 1, 0, [timestamp, value]);
        } else {
            // Add to the end of the array
            this.data.push([timestamp, value]);
        }

        this.maxValue = isNaN(this.maxValue) ? value : Math.max(this.maxValue, value);
        this.minValue = isNaN(this.minValue) ? value : Math.min(this.minValue, value);
    };

    TimeSeries.prototype.dropOldData = function(oldestValidTime, maxDataSetLength) {
        // We must always keep one expired data point as we need this to draw the
        // line that comes into the chart from the left, but any points prior to that can be removed.
        var removeCount = 0;
        while (this.data.length - removeCount >= maxDataSetLength && this.data[removeCount + 1][0] < oldestValidTime) {
            removeCount++;
        }
        if (removeCount !== 0) {
            this.data.splice(0, removeCount);
        }
    };

    /**
     * Initialises a new <code>SmoothieChart</code>.
     *
     * Options are optional, and should be of the form below. Just specify the values you
     * need and the rest will be given sensible defaults as shown:
     *
     * <pre>
     * {
     *   minValue: undefined,                      // specify to clamp the lower y-axis to a given value
     *   maxValue: undefined,                      // specify to clamp the upper y-axis to a given value
     *   maxValueScale: 1,                         // allows proportional padding to be added above the chart. for 10% padding, specify 1.1.
     *   minValueScale: 1,                         // allows proportional padding to be added below the chart. for 10% padding, specify 1.1.
     *   yRangeFunction: undefined,                // function({min: , max: }) { return {min: , max: }; }
     *   scaleSmoothing: 0.125,                    // controls the rate at which y-value zoom animation occurs
     *   millisPerPixel: 20,                       // sets the speed at which the chart pans by
     *   enableDpiScaling: true,                   // support rendering at different DPI depending on the device
     *   yMinFormatter: function(min, precision) { // callback function that formats the min y value label
     *     return parseFloat(min).toFixed(precision);
     *   },
     *   yMaxFormatter: function(max, precision) { // callback function that formats the max y value label
     *     return parseFloat(max).toFixed(precision);
     *   },
     *   maxDataSetLength: 2,
     *   interpolation: 'bezier'                   // one of 'bezier', 'linear', or 'step'
     *   timestampFormatter: null,                 // optional function to format time stamps for bottom of chart
     *                                             // you may use SmoothieChart.timeFormatter, or your own: function(date) { return ''; }
     *   scrollBackwards: false,                   // reverse the scroll direction of the chart
     *   horizontalLines: [],                      // [ { value: 0, color: '#ffffff', lineWidth: 1 } ]
     *   grid:
     *   {
     *     fillStyle: '#000000',                   // the background colour of the chart
     *     lineWidth: 1,                           // the pixel width of grid lines
     *     strokeStyle: '#777777',                 // colour of grid lines
     *     millisPerLine: 1000,                    // distance between vertical grid lines
     *     sharpLines: false,                      // controls whether grid lines are 1px sharp, or softened
     *     verticalSections: 2,                    // number of vertical sections marked out by horizontal grid lines
     *     borderVisible: true                     // whether the grid lines trace the border of the chart or not
     *   },
     *   labels
     *   {
     *     disabled: false,                        // enables/disables labels showing the min/max values
     *     fillStyle: '#ffffff',                   // colour for text of labels,
     *     fontSize: 15,
     *     fontFamily: 'sans-serif',
     *     precision: 2
     *   }
     * }
     * </pre>
     *
     * @constructor
     */
    function SmoothieChart(options) {
        this.options = Util.extend({}, SmoothieChart.defaultChartOptions, options);
        this.seriesSet = [];
        this.currentValueRange = 1;
        this.currentVisMinValue = 0;
        this.lastRenderTimeMillis = 0;
    }

    SmoothieChart.defaultChartOptions = {
        millisPerPixel: 20,
        enableDpiScaling: true,
        yMinFormatter: function(min, precision) {
            return parseFloat(min).toFixed(precision);
        },
        yMaxFormatter: function(max, precision) {
            return parseFloat(max).toFixed(precision);
        },
        maxValueScale: 1,
        minValueScale: 1,
        interpolation: 'bezier',
        scaleSmoothing: 0.125,
        maxDataSetLength: 2,
        scrollBackwards: false,
        grid: {
            fillStyle: '#ACACAC',
            strokeStyle: '#777777',
            lineWidth: 1,
            sharpLines: false,
            millisPerLine: 1000,
            verticalSections: 2,
            borderVisible: true
        },
        labels: {
            fillStyle: '#ffffff',
            disabled: false,
            fontSize: 10,
            fontFamily: 'monospace',
            precision: 2
        },
        horizontalLines: []
    };

    // Based on http://inspirit.github.com/jsfeat/js/compatibility.js
    SmoothieChart.AnimateCompatibility = (function() {
        var requestAnimationFrame = function(callback, element) {
                var requestAnimationFrame =
                    window.requestAnimationFrame ||
                    window.webkitRequestAnimationFrame ||
                    window.mozRequestAnimationFrame ||
                    window.oRequestAnimationFrame ||
                    window.msRequestAnimationFrame ||
                    function(callback) {
                        return window.setTimeout(function() {
                            callback(new Date().getTime());
                        }, 16);
                    };
                return requestAnimationFrame.call(window, callback, element);
            },
            cancelAnimationFrame = function(id) {
                var cancelAnimationFrame =
                    window.cancelAnimationFrame ||
                    function(id) {
                        clearTimeout(id);
                    };
                return cancelAnimationFrame.call(window, id);
            };

        return {
            requestAnimationFrame: requestAnimationFrame,
            cancelAnimationFrame: cancelAnimationFrame
        };
    })();

    SmoothieChart.defaultSeriesPresentationOptions = {
        lineWidth: 1,
        strokeStyle: '#ffffff'
    };

    /**
     * Adds a <code>TimeSeries</code> to this chart, with optional presentation options.
     *
     * Presentation options should be of the form (defaults shown):
     *
     * <pre>
     * {
     *   lineWidth: 1,
     *   strokeStyle: '#ffffff',
     *   fillStyle: undefined
     * }
     * </pre>
     */
    SmoothieChart.prototype.addTimeSeries = function(timeSeries, options) {
        this.seriesSet.push({
            timeSeries: timeSeries,
            options: Util.extend({}, SmoothieChart.defaultSeriesPresentationOptions, options)
        });
        if (timeSeries.options.resetBounds && timeSeries.options.resetBoundsInterval > 0) {
            timeSeries.resetBoundsTimerId = setInterval(
                function() {
                    timeSeries.resetBounds();
                },
                timeSeries.options.resetBoundsInterval
            );
        }
    };

    /**
     * Removes the specified <code>TimeSeries</code> from the chart.
     */
    SmoothieChart.prototype.removeTimeSeries = function(timeSeries) {
        // Find the correct timeseries to remove, and remove it
        var numSeries = this.seriesSet.length;
        for (var i = 0; i < numSeries; i++) {
            if (this.seriesSet[i].timeSeries === timeSeries) {
                this.seriesSet.splice(i, 1);
                break;
            }
        }
        // If a timer was operating for that timeseries, remove it
        if (timeSeries.resetBoundsTimerId) {
            // Stop resetting the bounds, if we were
            clearInterval(timeSeries.resetBoundsTimerId);
        }
    };

    /**
     * Gets render options for the specified <code>TimeSeries</code>.
     *
     * As you may use a single <code>TimeSeries</code> in multiple charts with different formatting in each usage,
     * these settings are stored in the chart.
     */
    SmoothieChart.prototype.getTimeSeriesOptions = function(timeSeries) {
        // Find the correct timeseries to remove, and remove it
        var numSeries = this.seriesSet.length;
        for (var i = 0; i < numSeries; i++) {
            if (this.seriesSet[i].timeSeries === timeSeries) {
                return this.seriesSet[i].options;
            }
        }
    };

    /**
     * Brings the specified <code>TimeSeries</code> to the top of the chart. It will be rendered last.
     */
    SmoothieChart.prototype.bringToFront = function(timeSeries) {
        // Find the correct timeseries to remove, and remove it
        var numSeries = this.seriesSet.length;
        for (var i = 0; i < numSeries; i++) {
            if (this.seriesSet[i].timeSeries === timeSeries) {
                var set = this.seriesSet.splice(i, 1);
                this.seriesSet.push(set[0]);
                break;
            }
        }
    };

    /**
     * Instructs the <code>SmoothieChart</code> to start rendering to the provided canvas, with specified delay.
     *
     * @param canvas the target canvas element
     * @param delayMillis an amount of time to wait before a data point is shown. This can prevent the end of the series
     * from appearing on screen, with new values flashing into view, at the expense of some latency.
     */
    SmoothieChart.prototype.streamTo = function(canvas, delayMillis) {
        this.canvas = canvas;
        this.delay = delayMillis;
        this.start();
    };

    /**
     * Make sure the canvas has the optimal resolution for the device's pixel ratio.
     */
    SmoothieChart.prototype.resize = function() {
        // TODO this function doesn't handle the value of enableDpiScaling changing during execution
        if (!this.options.enableDpiScaling || !window || window.devicePixelRatio === 1)
            return;

        var dpr = window.devicePixelRatio;
        var width = parseInt(this.canvas.getAttribute('width'));
        var height = parseInt(this.canvas.getAttribute('height'));

        if (!this.originalWidth || (Math.floor(this.originalWidth * dpr) !== width)) {
            this.canvas.setAttribute('width', (Math.floor(width * dpr)).toString());
            this.canvas.style.width = width + 'px';
            this.canvas.getContext('2d').scale(dpr, dpr);
        }

        if (!this.originalHeight || (Math.floor(this.originalHeight * dpr) !== height)) {
            this.originalHeight = height;
            this.canvas.setAttribute('height', (Math.floor(height * dpr)).toString());
            this.canvas.style.height = height + 'px';
            this.canvas.getContext('2d').scale(dpr, dpr);
        }
    };

    /**
     * Starts the animation of this chart.
     */
    SmoothieChart.prototype.start = function() {
        if (this.frame) {
            // We're already running, so just return
            return;
        }

        // Renders a frame, and queues the next frame for later rendering
        var animate = function() {
            this.frame = SmoothieChart.AnimateCompatibility.requestAnimationFrame(function() {
                this.render();
                animate();
            }.bind(this));
        }.bind(this);

        animate();
    };

    /**
     * Stops the animation of this chart.
     */
    SmoothieChart.prototype.stop = function() {
        if (this.frame) {
            SmoothieChart.AnimateCompatibility.cancelAnimationFrame(this.frame);
            delete this.frame;
        }
    };

    SmoothieChart.prototype.updateValueRange = function() {
        // Calculate the current scale of the chart, from all time series.
        var chartOptions = this.options,
            chartMaxValue = Number.NaN,
            chartMinValue = Number.NaN;

        for (var d = 0; d < this.seriesSet.length; d++) {
            // TODO(ndunn): We could calculate / track these values as they stream in.
            var timeSeries = this.seriesSet[d].timeSeries;
            if (!isNaN(timeSeries.maxValue)) {
                chartMaxValue = !isNaN(chartMaxValue) ? Math.max(chartMaxValue, timeSeries.maxValue) : timeSeries.maxValue;
            }

            if (!isNaN(timeSeries.minValue)) {
                chartMinValue = !isNaN(chartMinValue) ? Math.min(chartMinValue, timeSeries.minValue) : timeSeries.minValue;
            }
        }

        // Scale the chartMaxValue to add padding at the top if required
        if (chartOptions.maxValue != null) {
            chartMaxValue = chartOptions.maxValue;
        } else {
            chartMaxValue *= chartOptions.maxValueScale;
        }

        // Set the minimum if we've specified one
        if (chartOptions.minValue != null) {
            chartMinValue = chartOptions.minValue;
        } else {
            chartMinValue -= Math.abs(chartMinValue * chartOptions.minValueScale - chartMinValue);
        }

        // If a custom range function is set, call it
        if (this.options.yRangeFunction) {
            var range = this.options.yRangeFunction({
                min: chartMinValue,
                max: chartMaxValue
            });
            chartMinValue = range.min;
            chartMaxValue = range.max;
        }

        if (!isNaN(chartMaxValue) && !isNaN(chartMinValue)) {
            var targetValueRange = chartMaxValue - chartMinValue;
            var valueRangeDiff = (targetValueRange - this.currentValueRange);
            var minValueDiff = (chartMinValue - this.currentVisMinValue);
            this.isAnimatingScale = Math.abs(valueRangeDiff) > 0.1 || Math.abs(minValueDiff) > 0.1;
            this.currentValueRange += chartOptions.scaleSmoothing * valueRangeDiff;
            this.currentVisMinValue += chartOptions.scaleSmoothing * minValueDiff;
        }

        this.valueRange = {
            min: chartMinValue,
            max: chartMaxValue
        };
    };

    SmoothieChart.prototype.render = function(canvas, time) {
        var nowMillis = new Date().getTime();

        if (!this.isAnimatingScale) {
            // We're not animating. We can use the last render time and the scroll speed to work out whether
            // we actually need to paint anything yet. If not, we can return immediately.

            // Render at least every 1/6th of a second. The canvas may be resized, which there is
            // no reliable way to detect.
            var maxIdleMillis = Math.min(1000 / 6, this.options.millisPerPixel);

            if (nowMillis - this.lastRenderTimeMillis < maxIdleMillis) {
                return;
            }
        }

        this.resize();

        this.lastRenderTimeMillis = nowMillis;

        canvas = canvas || this.canvas;
        time = time || nowMillis - (this.delay || 0);

        // Round time down to pixel granularity, so motion appears smoother.
        time -= time % this.options.millisPerPixel;

        var context = canvas.getContext('2d'),
            chartOptions = this.options,
            dimensions = {
                top: 0,
                left: 0,
                width: canvas.clientWidth,
                height: canvas.clientHeight
            },
            // Calculate the threshold time for the oldest data points.
            oldestValidTime = time - (dimensions.width * chartOptions.millisPerPixel),
            valueToYPixel = function(value) {
                var offset = value - this.currentVisMinValue;
                return this.currentValueRange === 0 ?
                    dimensions.height :
                    dimensions.height - (Math.round((offset / this.currentValueRange) * dimensions.height));
            }.bind(this),
            timeToXPixel = function(t) {
                if (chartOptions.scrollBackwards) {
                    return Math.round((time - t) / chartOptions.millisPerPixel);
                }
                return Math.round(dimensions.width - ((time - t) / chartOptions.millisPerPixel));
            };

        this.updateValueRange();

        context.font = chartOptions.labels.fontSize + 'px ' + chartOptions.labels.fontFamily;

        // Save the state of the canvas context, any transformations applied in this method
        // will get removed from the stack at the end of this method when .restore() is called.
        context.save();

        // Move the origin.
        context.translate(dimensions.left, dimensions.top);

        // Create a clipped rectangle - anything we draw will be constrained to this rectangle.
        // This prevents the occasional pixels from curves near the edges overrunning and creating
        // screen cheese (that phrase should need no explanation).
        context.beginPath();
        context.rect(0, 0, dimensions.width, dimensions.height);
        context.clip();

        // Clear the working area.
        context.save();
        context.fillStyle = chartOptions.grid.fillStyle;
        context.clearRect(0, 0, dimensions.width, dimensions.height);
        context.fillRect(0, 0, dimensions.width, dimensions.height);
        context.restore();

        // Grid lines...
        context.save();
        context.lineWidth = chartOptions.grid.lineWidth;
        context.strokeStyle = chartOptions.grid.strokeStyle;
        // Vertical (time) dividers.
        if (chartOptions.grid.millisPerLine > 0) {
            context.beginPath();
            for (var t = time - (time % chartOptions.grid.millisPerLine); t >= oldestValidTime; t -= chartOptions.grid.millisPerLine) {
                var gx = timeToXPixel(t);
                if (chartOptions.grid.sharpLines) {
                    gx -= 0.5;
                }
                context.moveTo(gx, 0);
                context.lineTo(gx, dimensions.height);
            }
            context.stroke();
            context.closePath();
        }

        // Horizontal (value) dividers.
        for (var v = 1; v < chartOptions.grid.verticalSections; v++) {
            var gy = Math.round(v * dimensions.height / chartOptions.grid.verticalSections);
            if (chartOptions.grid.sharpLines) {
                gy -= 0.5;
            }
            context.beginPath();
            context.moveTo(0, gy);
            context.lineTo(dimensions.width, gy);
            context.stroke();
            context.closePath();
        }
        // Bounding rectangle.
        if (chartOptions.grid.borderVisible) {
            context.beginPath();
            context.strokeRect(0, 0, dimensions.width, dimensions.height);
            context.closePath();
        }
        context.restore();

        // Draw any horizontal lines...
        if (chartOptions.horizontalLines && chartOptions.horizontalLines.length) {
            for (var hl = 0; hl < chartOptions.horizontalLines.length; hl++) {
                var line = chartOptions.horizontalLines[hl],
                    hly = Math.round(valueToYPixel(line.value)) - 0.5;
                context.strokeStyle = line.color || '#ffffff';
                context.lineWidth = line.lineWidth || 1;
                context.beginPath();
                context.moveTo(0, hly);
                context.lineTo(dimensions.width, hly);
                context.stroke();
                context.closePath();
            }
        }

        // For each data set...
        for (var d = 0; d < this.seriesSet.length; d++) {
            context.save();
            var timeSeries = this.seriesSet[d].timeSeries,
                dataSet = timeSeries.data,
                seriesOptions = this.seriesSet[d].options;

            // Delete old data that's moved off the left of the chart.
            timeSeries.dropOldData(oldestValidTime, chartOptions.maxDataSetLength);

            // Set style for this dataSet.
            context.lineWidth = seriesOptions.lineWidth;
            context.strokeStyle = seriesOptions.strokeStyle;
            // Draw the line...
            context.beginPath();
            // Retain lastX, lastY for calculating the control points of bezier curves.
            var firstX = 0,
                lastX = 0,
                lastY = 0;
            for (var i = 0; i < dataSet.length && dataSet.length !== 1; i++) {
                var x = timeToXPixel(dataSet[i][0]),
                    y = valueToYPixel(dataSet[i][1]);

                if (i === 0) {
                    firstX = x;
                    context.moveTo(x, y);
                } else {
                    switch (chartOptions.interpolation) {
                        case "linear":
                        case "line": {
                            context.lineTo(x, y);
                            break;
                        }
                        case "bezier":
                        default: {
                            // Great explanation of Bezier curves: http://en.wikipedia.org/wiki/Bezier_curve#Quadratic_curves
                            //
                            // Assuming A was the last point in the line plotted and B is the new point,
                            // we draw a curve with control points P and Q as below.
                            //
                            // A---P
                            //     |
                            //     |
                            //     |
                            //     Q---B
                            //
                            // Importantly, A and P are at the same y coordinate, as are B and Q. This is
                            // so adjacent curves appear to flow as one.
                            //
                            context.bezierCurveTo( // startPoint (A) is implicit from last iteration of loop
                                Math.round((lastX + x) / 2), lastY, // controlPoint1 (P)
                                Math.round((lastX + x)) / 2, y, // controlPoint2 (Q)
                                x, y); // endPoint (B)
                            break;
                        }
                        case "step": {
                            context.lineTo(x, lastY);
                            context.lineTo(x, y);
                            break;
                        }
                    }
                }

                lastX = x;
                lastY = y;
            }

            if (dataSet.length > 1) {
                if (seriesOptions.fillStyle) {
                    // Close up the fill region.
                    context.lineTo(dimensions.width + seriesOptions.lineWidth + 1, lastY);
                    context.lineTo(dimensions.width + seriesOptions.lineWidth + 1, dimensions.height + seriesOptions.lineWidth + 1);
                    context.lineTo(firstX, dimensions.height + seriesOptions.lineWidth);
                    context.fillStyle = seriesOptions.fillStyle;
                    context.fill();
                }

                if (seriesOptions.strokeStyle && seriesOptions.strokeStyle !== 'none') {
                    context.stroke();
                }
                context.closePath();
            }
            context.restore();
        }

        // Draw the axis values on the chart.
        if (!chartOptions.labels.disabled && !isNaN(this.valueRange.min) && !isNaN(this.valueRange.max)) {
            var maxValueString = chartOptions.yMaxFormatter(this.valueRange.max, chartOptions.labels.precision),
                minValueString = chartOptions.yMinFormatter(this.valueRange.min, chartOptions.labels.precision),
                maxLabelPos = chartOptions.scrollBackwards ? 0 : dimensions.width - context.measureText(maxValueString).width - 2,
                minLabelPos = chartOptions.scrollBackwards ? 0 : dimensions.width - context.measureText(minValueString).width - 2;
            context.fillStyle = chartOptions.labels.fillStyle;
            context.clearRect(0, 0, context.measureText(maxValueString).width + 4, dimensions.height);
            context.save();
            context.lineWidth = chartOptions.grid.lineWidth;
            context.strokeStyle = chartOptions.grid.strokeStyle;
            context.beginPath();
            context.moveTo(context.measureText(maxValueString).width + 4, 0);
            context.lineTo(context.measureText(maxValueString).width + 4, dimensions.height);
            context.lineTo(dimensions.width, dimensions.height);
            context.stroke();
            context.closePath();
            context.restore();
            //context.fillText(maxValueString, 2, chartOptions.labels.fontSize);
            //context.fillText(minValueString/2, 2, dimensions.height - 2);
            var i = (parseFloat(maxValueString) - parseFloat(minValueString)) / chartOptions.grid.verticalSections;
            var h = dimensions.height / chartOptions.grid.verticalSections;
            if (chartOptions.yMaxFormatter(this.valueRange.min, chartOptions.labels.precision) != chartOptions.yMaxFormatter(this.valueRange.min + i, chartOptions.labels.precision))
                for (var p = 0; p < chartOptions.grid.verticalSections; p++) {
                    context.fillText(chartOptions.yMaxFormatter(this.valueRange.min + (p * i), chartOptions.labels.precision), 2, dimensions.height - (p * h));
                }
        }

        // Display timestamps along x-axis at the bottom of the chart.
        if (chartOptions.timestampFormatter && chartOptions.grid.millisPerLine > 0) {
            var textUntilX = chartOptions.scrollBackwards ?
                context.measureText(minValueString).width :
                dimensions.width - context.measureText(minValueString).width + 4;
            for (var t = time - (time % chartOptions.grid.millisPerLine); t >= oldestValidTime; t -= chartOptions.grid.millisPerLine) {
                var gx = timeToXPixel(t);
                // Only draw the timestamp if it won't overlap with the previously drawn one.
                if ((!chartOptions.scrollBackwards && gx < textUntilX) || (chartOptions.scrollBackwards && gx > textUntilX)) {
                    // Formats the timestamp based on user specified formatting function
                    // SmoothieChart.timeFormatter function above is one such formatting option
                    var tx = new Date(t),
                        ts = chartOptions.timestampFormatter(tx),
                        tsWidth = context.measureText(ts).width;

                    textUntilX = chartOptions.scrollBackwards ?
                        gx + tsWidth + 2 :
                        gx - tsWidth - 2;

                    context.fillStyle = chartOptions.labels.fillStyle;
                    if (chartOptions.scrollBackwards) {
                        context.fillText(ts, gx, dimensions.height - 2);
                    } else {
                        context.fillText(ts, gx - tsWidth, dimensions.height - 2);
                    }
                }
            }
        }

        context.restore(); // See .save() above.
    };

    // Sample timestamp formatting function
    SmoothieChart.timeFormatter = function(date) {
        function pad2(number) {
            return (number < 10 ? '0' : '') + number
        }
        return pad2(date.getHours()) + ':' + pad2(date.getMinutes()) + ':' + pad2(date.getSeconds());
    };

    exports.TimeSeries = TimeSeries;
    exports.SmoothieChart = SmoothieChart;

})(typeof exports === 'undefined' ? this : exports);